(a) Field of the Invention
The present invention relates to a cathode-ray tube (CRT) having a faceplate panel and, more particularly, to a CRT faceplate panel for producing a uniform and clear visual image across the entire area of a viewing screen.
(b) Description of the Related Art
Generally, CRTs are designed to reproduce a picture image on a screen of a faceplate panel by exciting phosphors coated on an interior surface of the faceplate panel with electron beams emitted from an electron gun and passing through apertures of a color-selecting shadow mask. The shadow mask ensures that each electron beam lands on the correct phosphor.
The faceplate panel is usually formed with a transparent glass plate having curved interior and exterior surfaces. These curved surfaces enable the panel to withstand the high-vacuum pressure in the CRT and facilitate the landing of the electron beams on the phosphor screen.
However, such a faceplate panel involves a relatively broad light-reflecting exterior area in peripheral portions thereby, deteriorating the brightness of those areas and distorting the appearance of the picture.
To remedy this problem, a glass plate having flat interior and exterior surfaces for the CRT faceplate panel has been developed. Such a panel employs a flat tension mask to perform the color-selecting function, the flat tension mask corresponding to the flat interior surface of the panel. The flat tension mask has predetermined horizontal and vertical tensional strengths to prevent the occurrence of a doming phenomenon.
However, in this type of panel, the visual images realized through the phosphor screen and refracted on the panel appear depressed to the user in the center portion of the viewing screen. The problem becomes more severe with larger-sized screens.
To overcome this drawback, Japanese Patent Laid-Open Publication Nos. Hei 6-44926 and 6-36710 introduce a CRT faceplate panel which is flat on an exterior surface but curved on an interior surface. However, the images realized through these inventions appear bulged outward. Further, because the peripheral portions of the panel are considerably thicker than center portions, the brightness of the screen is deteriorated.
It is an object of an embodiment of the present invention to provide a CRT faceplate panel for producing a uniform visual image across the entire area of a viewing screen.
It is another object of an embodiment of the present invention to provide a CRT faceplate panel having an optimum light transmission rate to realize a clear visual image across the viewing screen.
It is still another object of an embodiment of the present invention to provide a CRT having a faceplate panel for producing a clear visual image across the viewing screen.
In order to achieve these objects and others, an embodiment of the CRT faceplate panel includes an exterior surface having a substantially flat shape, and an interior surface having a concave shape. The interior surface curves in a direction toward the flat exterior surface with a diagonal curvature radius Rp satisfying the following condition:
1.2Rxe2x89xa6Rpxe2x89xa68R,
where R=1.767xc3x97the diagonal length of the effective screen of the CRT. Furthermore, a peripheral thickness t of the faceplate panel at the diagonal end of the effective screen satisfies the following condition:
Bxe2x89xa6txe2x89xa6A,
where B is the peripheral thickness of the panel at the diagonal end of the effective screen when a diagonal curvature radius Rp of the interior surface is 8R, and A is the peripheral thickness of the panel at the diagonal end of the effective screen when the ratio of the light transmission at the peripheral portion at the diagonal end of the effective screen to the light transmission at the central portion of the effective screen is 0.85.
The described embodiment CRT includes a faceplate panel having a flat exterior surface and a curved interior surface, a funnel sealed to the rear of the faceplate panel, a shadow mask placed behind the faceplate panel, an electron gun mounted within a neck portion of the funnel, and a deflection yoke placed around an outer periphery of the funnel.
The shadow mask has a diagonal curvature radius R8 satisfying the following condition.
1.2Rxe2x89xa6R8xe2x89xa64R
where R=1.767xc3x97the diagonal length of effective screen of the CRT.
The interior surface of the faceplate panel has a diagonal curvature radius Rp satisfying the following condition:
xe2x80x831.2Rxe2x89xa6Rpxe2x89xa64R,
where R=1.767xc3x97the diagonal length of effective screen of the CRT.